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copied!<p><code>stdout=None</code> means, the <code>stdout</code>-handle from the process is directly inherited from the parent, in easier words it basically means, it gets printed to the console (same applies for <code>stderr</code>).</p> <p>Then you have the option <code>stderr=STDOUT</code>, this redirects <code>stderr</code> to the <code>stdout</code>, which means the output of <code>stdout</code> and <code>stderr</code> are forwarded to the same file handle.</p> <p>If you set <code>stdout=PIPE</code>, Python will redirect the data from the process to a new file handle, which can be accessed through <code>p.stdout</code> (<code>p</code> beeing a <code>Popen</code> object). You would use this to capture the output of the process, or for the case of <code>stdin</code> to send data (constantly) to <code>stdin</code>. But mostly you want to use <code>p.communicate</code>, which allows you to send data to the process once (if you need to) and returns the complete <code>stderr</code> and <code>stdout</code> if the process is completed!</p> <p>One more interesting fact, you can pass any <code>file-object</code> to <code>stdin/stderr/stdout</code>, e.g. also a file opened with <code>open</code> (the object has to provide a <code>fileno()</code> method).</p> <p>To your <code>wait</code> problem. This should not be the case! As workaround you could use <code>p.poll()</code> to check if the process did exit! What is the return-value of the <code>wait</code> call?</p> <p><a href="http://docs.python.org/2/library/subprocess.html#frequently-used-arguments" rel="noreferrer">Furthermore, you should avoid <code>shell=True</code> especially if you pass user-input as first argument</a>, this could be used by a malicious user to exploit your program! Also it launches a shell process which means additional overhead. Of course there is the 1% of cases where you actually need <code>shell=True</code>, I can't judge this with your minimalistic example.</p>

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